Effects of Weaning Age and Antibiotic Use on Pig Performance in a Commercial System

A total of 2,184 barrows and gilts (DNA 600 × PIC L42) were used in a study from weaning to market to evaluate the effect of increasing weaning age and antibiotic use on pig performance in a commercial production system. A 3 × 2 factorial arrangement was used. The treatments included weaning age (18.5, 21.5, or 24.5 days of age) and the use of antibiotic (AB) or antibiotic free (ABF). There were 14 replicate pens per treatment and 26 pigs per pen (13 barrows and 13 gilts). Pigs were weaned from a 4,000-sow farm and placed in pens by weaning age with pens randomly assigned to AB or ABF. Pigs assigned to AB had access to a diet containing 400 ppm of chlortetracycline (CTC) from d 8 to 21 post-weaning, and after a porcine respiratory and reproductive syndrome (PRRS) outbreak at week 7 post-weaning, they were medicated via drinking water for five consecutive days with CTC (10 mg/lb of body weight (BW) per day). For the first 42 days post-weaning, increasing weaning age reduced the number of pigs treated with injectable antibiotic (quadratic, P = 0.004), but AB use did not influence this variable (P = 0.626). Each additional day of weaning age resulted in greater BW at weaning and at 197 days of age with slopes of 0.484 lb and 1.485 lb, respectively (linear, P \u3c 0.001). From weaning to 197 days of age, increasing weaning age increased average daily gain (0.02 lb/day of weaning age; linear, P \u3c 0.001) and the same effect was found for AB (0.03 lb/d; P = 0.009). Weaning age and AB also affected average daily feed intake (0.03 lb/day of increase in weaning age; linear, P \u3c 0.001 and 0.08 lb/d; P = 0.031, respectively). An interaction (linear, P = 0.005) was found for feed efficiency. When AB were fed, pigs weaned at 21.5 and 24.5 d were less efficient. However, AB improved feed efficiency of pigs weaned at 18.5 d. Pigs with access to AB in feed and water had lower total losses (2.7% less mortality + removal; P \u3c 0.001). Increasing weaning age also marginally decreased total losses (-0.21% per day increase in weaning age; linear, P = 0.097). The weight sold (at 197 d of age) per pig weaned was increased by increasing weaning age (an additional 1.55 lb for each day increase in weaning age; linear, P = 0.050) and by using AB in feed and water (an addition of 10.1 lb/pig; P = 0.019). In summary, increasing weaning age linearly improved pig performance and relatively short-term use of antibiotics reduced mortality and removals. In addition, both factors contributed to maximizing the weight sold per pig weaned

Effects of Corn Dried Distillers Grains with Solubles Withdrawal on Finishing Pig Performance

A total of 860 finishing pigs [C48 or L42 × 327; initially 146 ± 11.1 lb body weight (BW)] were used in a 76-d experiment to evaluate the effects of removing corn dried distillers grains with solubles (DDGS) from diets at varying intervals before harvest. Pigs were fed diets containing 40% DDGS until the start of the trial. Diets contained 35% DDGS from approximately 146 to 180 lb and 30% until the completion of the trial. Pen served as the experimental unit, and there were 7 replicate pens per treatment with 23 to 25 pigs per pen. Pens were blocked by BW within the barn and allotted to 1 of 5 dietary treatments differentiated by the number of days before slaughter that diets containing DDGS were withdrawn and replaced with corn-soybean meal-based diets. Withdrawal times consisted of the following: 76 (no DDGS fed), 42, 27, 15, or 0 d (no withdrawal) before the time all pigs were marketed. At the time of harvest, all pigs were sent to a commercial processing facility for carcass data collection. For the overall period from d -76 to 0, as time of DDGS withdrawal increased, average daily gain (ADG) and final BW also increased (linear, P \u3c 0.018), while feed:gain ratio (F/G) improved (quadratic, P = 0.022). Average daily feed intake (ADFI) quadratically decreased (P = 0.030) with increasing withdrawal time. There was a linear increase (P = 0.009) in hot carcass weight (HCW), with a marginally significant increase in carcass yield (linear, P = 0.094) with increasing DDGS withdrawal time. Loin depth and lean percentage did not demonstrate any evidence for treatment differences (P \u3e 0.132). Backfat was linearly increased (P = 0.030) with a marginally significant (P = 0.084) quadratic response with increasing DDGS withdrawal time. Lastly, the iodine value of belly fat was increased (linear, P \u3c 0.034) with increased feeding duration of DDGS. Feed cost per pig and income over feed cost (IOFC) per all pigs that started on the experiment were increased (linear, P \u3c 0.048) with increasing withdrawal time. Feed cost per lb of gain did not demonstrate evidence for treatment differences (P \u3e 0.505). When based on the number of pigs marketed at the end of the experiment, feed cost per pig was increased (linear, P = 0.001) with increasing withdrawal time, though feed cost per lb of gain and IOFC did not have evidence for differences (P \u3e 0.186). Carcass gain value was increased (linear, P = 0.001) with increased DDGS withdrawal time. In conclusion, removing pigs from DDGS for longer periods before slaughter increased ADG and improved F/G, resulting in increased HCW. Belly fat iodine value was inversely related to the length of DDGS withdrawal, with the highest iodine value (IV) resulting from pigs that consumed DDGS for the entire finishing period. The advantages in final BW and HCW seen in the present data may encourage producers to remove DDGS from finishing diets earlier than commonly practiced

Effects of Mat Feeding on the Growth Performance and Mortality of Pigs After Weaning

Three experiments were conducted to determine the effect of different mat feeding strategies on the growth performance and morbidity and mortality of pigs after weaning. Upon arrival to the nursery facility, pigs were randomized to pen. A total of 96 pens (48 feeders) with 30 to 35 pigs/pen were used for each experiment, with one barrow pen and one gilt pen per feeder. Thus, feeder (2 pens) was the experimental unit. Feeders were then blocked by group (date of placement) and randomly allotted to treatment. In Exp. 1, treatments consisted of two feed management strategies; mat feeding vs. no mat feeding. Overall, a tendency was observed for ADG (P = 0.056) with mat fed pigs having poorer ADG compared to the control group, which resulted in decreased (P \u3c 0.026) final body weights. No differences were observed in ADFI or feed efficiency. Mat fed pigs had reduced total removals (P = 0.019) compared to the control group. In Exp. 2, treatments were arranged in a 2 × 2 factorial with main effects of diet form (pellet or crumble) and mat feeding (without or with). No interactions between diet form and mat feeding were observed. No differences were observed in overall growth performance for the main effect of mat feeding, but for diet form, pigs that received pelleted feed had decreased overall ADFI (P = 0.013) and improved feed efficiency (P \u3c 0.001). No differences were observed in total removals. In Exp. 3, treatments consisted of three feed management strategies: mat feeding small (1/8 in.) pellets, mat feeding large (1/2 in.) pellets, and no mat feeding. No differences were observed in overall ADG or feed efficiency; however, mat fed pigs had increased ADFI (P \u3c 0.05), regardless of pellet size. Although not statistically significant, mat feeding the small pellets reduced the total removal rate by 2.1 percentage points compared to the control group, and 1.2 percentage points compared to mat feeding the large pellets. When combining the removal and mortality data for the three experiments, mat fed pigs had fewer total removals (P = 0.025) compared to the control group. In summary, mat feeding has limited effects on the growth performance of pigs after weaning; however, mat feeding may encourage earlier feed intake, therefore reducing the morbidity and mortality rate of pigs

Effect of Floor Feeding Creep Feed on the Growth Performance and Mortality of Pigs After Weaning

A total of 264 litters (PIC × Duroc (n = 180) or Choice Genetics × Duroc (n = 84)) corresponding to 2,497 nursery pigs were used in a 40-d trial (4-d pre-weaning and 36-d post-weaning) to determine the effect of floor feeding different pellet sizes of creep feed or lactation feed on the growth performance and mortality of pigs after weaning. Treatments were applied in the farrowing house for 4 d prior to weaning and consisted of a control (no creep feed), standard (1/8 in.) creep pellet, large (1/2 in.) creep pellet, or sow lactation feed. For each treatment, approximately 0.50 lb of creep feed per day, equally divided into 2 feedings (AM and PM) was provided on the mat in farrowing stalls. At weaning (approximately d 19 of age), pigs were transported to the nursery facility and randomized to pen within creep feeding treatment group. A total of 96 pens (48 feeders) were used, with one barrow pen and one gilt pen per feeder. Thus, feeder (2 pens) was the experimental unit. There were 26 pigs per pen (52 pigs per feeder) and 12 replications per creep feeding treatment. For creep feeding during lactation, floor feeding different pellet size creep feed or lactation feed had no effects on the percentage of piglets that consumed creep feed (eaters). For the first week post-weaning, pigs fed standard or large pellet creep feed had increased (P \u3c 0.001) ADG compared to pigs fed sow lactation feed or no creep feed. However, this was not driven by an improvement in ADFI. This resulted in an improved (P \u3c 0.001) F/G for pigs fed large pellet creep feed compared to pigs fed sow lactation feed or no creep feed, with pigs fed standard pellet creep feed intermediate. No differences in ADG, ADFI, or F/G were observed throughout the remainder of the nursery period. On a per pig placed basis, pigs fed large pellet creep feed had increased total BW gain (P = 0.024), ADG (P = 0.027), and improved F/G (P = 0.021) compared to pigs fed sow lactation feed, with the other two treatment groups intermediate. This response was a direct reflection of decreased (P = 0.050) total removal rate for pigs fed large pellet creep feed. In summary, floor feeding large pellet creep feed in lactation appears to improve nursery pig growth performance and fallout rates compared to creep feeding sow lactation feed, with standard pellet creep feed or no creep feed having an intermediate effect

The Effect of Increased Pork Hot Carcass Weights on Consumer Palatability Ratings of Top Loin Chops

The objective of this study was to evaluate the effects of pork hot carcass weight on consumer palatability ratings of top loin chops. Pork loins (n = 200) were collected from 4 different hot carcass weight groups: light weight group (less than 246.5 lb; LT), medium-light weight group (246.5 to 262.5 lb; MLT), medium-heavy weight group (262.5 to 276.5 lb; MHVY), and a heavy weight group (276.5 lb and greater; HVY). Instrumental color, visual color and marbling, and pH were taken for each loin prior to fabrication. Loins from all weight groups differed (P \u3c 0.05) in weight (LT \u3c MLT \u3c MHVY \u3c HVY). No carcass weight effects (P \u3e 0.05) were found for loin instrumental color, subjective color, subjective marbling, purge loss, and pH. Carcass weight did not affect (P \u3e 0.05) juiciness, flavor, or overall like ratings, but did affect (P \u3c 0.05) tenderness ratings. Chops from the HVY group were rated as more (P \u3c 0.05) tender compared to chops from the LT weight group. Weight group did not contribute (P \u3e 0.05) to the percentage of chops rated acceptable for flavor and overall like. The greatest (P \u3c 0.05) percentage of samples were rated acceptable for juiciness for chops from the HVY weight group, and the lowest (P \u3c 0.05) percentage of acceptable ratings for tenderness for chops were from the LT weight group. Consumers perceived the lowest (P \u3c 0.05) percentage of chops from the HVY group as unsatisfactory quality in comparison to chops from the 2 lightest weight groups. Weight did not contribute (P \u3e 0.05) to consumer quality ratings. These results indicate top loin chops from heavier weight carcasses have improved tenderness compared to chops from lighter carcasses

The Effect of Increased Pork Hot Carcass Weights and Chop Thickness on Consumer Visual Appearance and Purchase Intent Ratings of Top Loin Chops

The objective of this study was to evaluate the effect of increased pork hot carcass weights on consumer visual acceptability and purchase intent of top loin chops cut to various thicknesses in a price labeled versus unlabeled retail display scenario. Pork loins (n = 200) were collected from 4 different hot carcass weight groups: a light weight group (less than 246.5 lb; LT), medium light weight group (246.5 to 262.5 lb; MLT), medium heavy weight group (262.5 lb to 276.5 lb; MHVY), and heavy weight group (276.5 lb and greater; HVY). Loins were fabricated into 4 pairs of chops of specified thicknesses (0.50, 0.75, 1.00, and 1.25 inches) at day 7, 8, and 9 postmortem. One chop from each specified thickness was then randomly assigned to be packaged with a label and the other to be packaged without a label. Consumers (n = 393; 8/panel) from the Manhattan, KS, area assessed chops from each weight group × thickness combination in both labeled and unlabeled scenarios. Chops were assessed on a 1 to 100 continuous line scale for desirability and purchase intent. Consumers were also able to indicate if the chop was either desirable or undesirable and if they would or would not purchase. Consumers gave greater (P \u3c 0.05) appearance ratings to chops from HVY and MHVY weight group compared to chops from the LT weight group. Additionally, chops with a thickness of 1.00 and 1.25 were similar (P \u3e 0.05) and had greater (P \u3c 0.05) consumer appearance ratings than both 0.75- and 0.50-inch chops. For purchase intent ratings, consumers gave greater (P \u3c 0.05) ratings to chops from HVY and MHVY carcasses compared to chops from LT carcasses. Consumers gave chops with a thickness of 0.50 inches the lowest (P \u3c 0.05) purchase intent ratings compared to all other thicknesses. There was a carcass weight × chop thickness interaction (P \u3c 0.05) for the percentage of consumers who indicated “Yes” the chop was desirable overall. For all weight treatments, 0.50-inch chops had the lowest (P \u3c 0.05) percentage of consumers who indicated the chop was desirable. A greater (P \u3c 0.05) percentage of consumers indicated they would purchase 1.00-inch chops compared to all other thicknesses, with 0.75- and 1.25-inch chops intermediate (1.00 \u3e 0.75 \u3e 1.25 \u3e 0.50). Additionally, a greater (P \u3c 0.05) percentage of consumers indicated they would purchase unlabeled chops compared to labeled chops. These results indicate that carcass weight and chop thickness can affect consumer preference and purchasing decisions and thus should be considered by retailers when marketing fresh pork loin chops

Effects of Space Allowance and Marketing Strategy on Growth Performance of Pigs Raised to Heavy Market Weights

A total of 976 pigs (PIC 327 × L42, initially 48.6 ± 3.4 lb body weight [BW]) were used in a 160-d growth study to determine the influence of space allowance and marketing strategy on growth performance of pigs raised to heavy market weights. Pens were blocked by location within the barn and allotted to 1 of 6 dietary treatments with 8 pens per treatment. The first four treatments reduced space allowance per pig via initial pen stocking density and had only one final marketing event. These four treatments were: 14 pigs/pen (12.7 ft2/pig), 17 pigs/pen (10.4 ft2/pig), 20 pigs/pen (8.8 ft2/pig), 23 pigs/pen (7.7 ft2/pig). The fifth treatment began with 25 pigs/pen (7.1 ft2/pig) and the heaviest 3 pigs/pen were removed on d 93, then on d 122 they were topped again to a common inventory of 20 pigs/pen, and on d 147 topped to a common pen inventory of 17 pigs/pen. The sixth treatment began with 23 pigs/pen (7.7 ft2/pig) and was topped to a common inventory of 20 pigs/pen on d 108 and finally topped again to a common inventory of 17 pigs/pen on d 147. Average daily gain (ADG), average daily feed intake (ADFI), and final BW decreased (linear, P \u3c 0.001) during the overall experimental period (d 0 to 160) as space allowance decreased. When comparing treatments with multiple marketing events to those with similar initial stocking density (23 pigs per pen), there was no evidence for differences (P \u3e 0.05) for overall ADG or ADFI; however, overall feed efficiency was improved (P \u3c 0.05) for pigs initially stocked at 7.1 ft2/pig and marketed four times compared to both treatments that initially allowed 7.7 ft2/pig, regardless of marketing structure. Additionally, overall F/G was improved for pigs that began at 7.7 ft2/pig and had 3 marketing events compared to the treatment that also began at 7.7 ft2/pig but had only a single marketing event. Once the marketing events began on d 93, ADG and F/G were improved (P \u3c 0.05) for the remaining pigs in the pen for the rest of the trial (d 93 to 160) for both multiple marketing treatments, compared to the 7.7 ft2/pig allowance where all pigs were marketed together at the end of the trial. These findings are consistent with others that evaluate more traditional market weights where growth performance is reduced prior to pigs reaching their k-value, and align with recent models that predict the rate of change in growth performance as pigs are allowed more spacing during the finishing period. Similarly, it appears that pigs respond to removal of the heaviest pigs in the pen before market with the remaining pigs in the pen demonstrating compensatory gain after being provided with increased space. These results indicate that decreasing space allowance for heavy weight pigs reduced growth, intake, and final BW, although use of pig removals prior to final marketing may allow producers to maximize number of pigs marketed while balancing reduced growth performance generally accompanied with increased stocking density. Additionally, growth continued to increase until approximately 340 lb, indicating a potential opportunity for swine producers to capture lean growth at much heavier weights than previously predicted

Comparison between the HCV IRES domain IV RNA structure and the Iron Responsive Element

Background: Serum ferritin and hepatic iron concentrations are frequently elevated in patients who are chronically infected with the hepatitis C virus (HCV), and hepatic iron concentration has been used to predict response to interferon therapy, but these correlations are not well understood. The HCV genome contains an RNA structure resembling an iron responsive element (IRE) in its internal ribosome entry site (IRES) structural domain IV (dIV). An IRE is a stem loop structure used to control the expression of eukaryotic proteins involved in iron homeostasis by either inhibiting ribosomal binding or protecting the mRNA from nuclease degradation. The HCV structure, located within the binding site of the 40S ribosomal subunit, might function as an authentic IRE or by an IRE-like mechanism.----- Results: Electrophoretic mobility shift assays showed that the HCV IRES domain IV structure does not interact with the iron regulatory protein 1 (IRP1) in vitro. Systematic HCV IRES RNA mutagenesis suggested that IRP1 cannot accommodate the shape of the wild type HCV IRES dIV RNA structure.----- Conclusion The HCV IRES dIV RNA structure is not an authentic IRE. The possibility that this RNA structure is responsible for the observed correlations between intracellular iron concentration and HCV infection parameters through an IRE-like mechanism in response to some other cellular signal remains to be tested

RNAi for Treating Hepatitis B Viral Infection

Chronic hepatitis B virus (HBV) infection is one of the leading causes of liver cirrhosis and hepatocellular carcinoma (HCC). Current treatment strategies of HBV infection including the use of interferon (IFN)-α and nucleotide analogues such as lamivudine and adefovir have met with only partial success. Therefore, it is necessary to develop more effective antiviral therapies that can clear HBV infection with fewer side effects. RNA interference (RNAi), by which a small interfering RNA (siRNA) induces the gene silence at a post-transcriptional level, has the potential of treating HBV infection. The successful use of chemically synthesized siRNA, endogenous expression of small hairpin RNA (shRNA) or microRNA (miRNA) to silence the target gene make this technology towards a potentially rational therapeutics for HBV infection. However, several challenges including poor siRNA stability, inefficient cellular uptake, widespread biodistribution and non-specific effects need to be overcome. In this review, we discuss several strategies for improving the anti-HBV therapeutic efficacy of siRNAs, while avoiding their off-target effects and immunostimulation. There is an in-depth discussion on the (1) mechanisms of RNAi, (2) methods for siRNA/shRNA production, (3) barriers to RNAi-based therapies, and (4) delivery strategies of siRNA for treating HBV infection